The investigation of neochloris oleoabundans biomass as potential substrate for microbial fuel cell / Muhammad Haikal Zainal

The microalgae-Microbial Fuel Cells (mMFCs) is a promising electricity provider because of microalgae biomass as a substrate in Microbial Fuel Cells (MFCs) is able to generate higher maximum power density compared to other substrates, such as glucose, acetate and etc. Common microalgae biomass species used in mMFCs is high lipid content Chlorella vulgaris, which also contains recalcitrant cellulose in their cell wall structure –a hindrance for enzyme attack, thus resisting biodegradation which could affect the performance of MFC. Alternatively, a green algae species which reported has higher lipid content than Chlorella vulgaris is Neochloris oleoabundans, which has not been yet reported in mMFCs researches. Neochloris oleoabundans biomass is demonstrated in this study to generate bioelectricity and evaluate its performance. In order to generate bioelectricity for a long-term operation, a special and high-end MFC reactor configuration is required. Two types of MFC design has been fabricated which are Double Chamber MFC (dMFC) and Single Chamber MFC (sMFC). The difference between the two MFCs are their cathode configuration, where dMFC was using aqueous-aerated cathode design while sMFC was using air-cathode design. Both prototype MFCs were demonstrated with a mixture bioelectrolyte solution of sampled activated sludge as inoculum, Phosphate Buffer Saline (PBS) medium and Chlorella vulgaris biomass powder as substrate. As a result, the sMFC produced 18 times higher maximum power density than dMFC. However, the power output still lower than other mMFC researches due to lack some modifications. Thus, a new prototype MFC based on sMFC configuration was modified and improved, such as small size, lightweight, and low internal resistance, is known as sandwich type MFC (pMFC). The special and high-end pMFC design was demonstrated with microalgae biomass species, Neochloris oleoabundans about 25.87 ± 2.16 W.m-2 in a triplicate and multiple cycles of operation. The Chemical Oxygen Demand (COD) removal percentage was 64.7 ± 16.4 %, while Coulombic Efficiency was 33.9 ± 20.2 %. The internal resistance of pMFCs system was 12.78 kΩ cm2. Consequently, Neochloris oleoabundans biomass did generate bioelectricity greater than the Chlorella vulgaris biomass. The analysis through variation of Neochloris oleoabundans biomass concentrations of 1.0 g/L, 2.5 g/L and 5.0 g/L showed that the trend of maximum power densities produced was increased as the biomass concentration increased, due to increase of ionic concentration present in the anodic solution. The study of effect of biomass pre-treatment also showed that a completely pulverized microalgal cell walls able to facilitate microbial lipid digestion and improved the bioelectricity generation. Furthermore, the statistical analysis showed its reproducibility results which is the P-value was greater than α = 0.05, suggested that there was no significant difference between maximum power densities from variations of different microalgae biomasses over fed-batch cycles of operation of pMFCs. Therefore, the performance of Neochloris oleoabundans biomass based pMFCs (NbMs) is a potential alternative source in the practical applications and commercialization of microbial fuel cell technology as alternative energy provider.